The present invention relates to a method of winding a secondary coil of an engine igniting coil device.
Japanese laid-open patent No. 60-107813 discloses a bank winding method applied for manufacturing a secondary coil of a compact engine ignition coil device having a necessary dielectric strength of the coil interlayer insulation. According to this bank winding method, an element wire being fed from a nozzle reciprocating in the coil winding direction for a distance of a specified width is suitably tensioned and wound spirally in banks of turns one by one in both forward and reverse directions on a coil bobbin coaxially connected to a rotating shaft.
The conventional bank winding method forms a coil on a coil bobbin by winding an element wire in layers around the bobbin in both forward and reverse directions by the reciprocal movement of the nozzle in parallel to the longitudinal axis of the bobbin. Consequently, a nozzle-to-bobbin distance (distance from a nozzle tip to a bending point of an element wire to form a new turn of a coil on the bobbin) and a wire-to-nozzle angle (angle formed by the element wire with the nozzle outlet axis) varies according to the changing radius of a coil being formed on the bobbin, causing fluctuation of tension in the element wire.
In short, the conventional bank winding method applied for manufacturing an engine ignition coil device has the following problems to be solved.
The first problem of the conventional bank winding method for winding an element wire in banks of turns around a coil bobbin by using a nozzle reciprocating parallel to the longitudinal axis of the coil bobbin is that the nozzle-to-bobbin distance and the wire-to-nozzle angle vary and make the tension of the wire unstable, resulting in loosening and/or falling-down of wire turns of the coil.
The second problem is that the conventional bank-winding method may be accompanied by a remarkable variation of the nozzle-to-bobbin distance and the wire-to-nozzle angle, in particular, when winding a tensioned fine element wire (e.g., a wire of 0.05 to 0.07 mm in diameter) in banks of turns one over another around the coil bobbin in both forward and backward directions. In this case, the fine wire unsteadily oscillates in a relatively large outlet of the nozzle, causing the falling-down of the turns in the coil being formed on the bobbin.